JP5000814B2

JP5000814B2 - Method for removing impurities in ethyl lactate

Info

Publication number: JP5000814B2
Application number: JP2001207068A
Authority: JP
Inventors: 道彦五月女
Original assignee: Toho Chemical Industry Co Ltd
Current assignee: Toho Chemical Industry Co Ltd
Priority date: 2001-06-05
Filing date: 2001-06-05
Publication date: 2012-08-15
Anticipated expiration: 2021-06-05
Also published as: JP2002363135A

Description

【０００１】
【発明の属する技術分野】
本発明は、カルボジイミド類、及びアニリン誘導体を用い蒸留することによって、醗酵法により製造された乳酸エチル中の酸度、及び２７０ｎｍ以上、４００ｎｍ以下のＵＶ吸光度を低減させることを特徴とするフォトレジスト用溶剤として有用な乳酸エチルの精製方法に関する。或いは、醗酵乳酸エチルをアニリン誘導体の存在下、蒸留することによって、２７０ｎｍ以上、４００ｎｍ以下のＵＶ吸光度を低減させることを特徴とする乳酸エチルの精製方法に関する。
【０００２】
【従来の技術】
乳酸エチルは、リソグラフィ技術を利用して製造される半導体デバイス、プリント配線板あるいは印刷版等の広範囲な分野で用いられるフォトレジスト樹脂溶剤として使用されている。ところが、醗酵法により製造された乳酸エチルの欠点は、微量の不純物、例えば酢酸、乳酸等の酸度原因物質や種々カルボニル化合物等のＵＶ吸収原因物質が存在することであり、これらの微量の不純物は、従来の精製手段、例えば、単なる蒸留のみでは実質的に除去することは出来ない。
【０００３】
もし、酸度原因物質がポジ型フォトレジスト樹脂溶剤中に存在しており、ベーク時に蒸発せず、濃縮されたとすると、アルカリ水溶液等の現像液により未露光部分が溶解されて、不良パターンとなる可能性がある。また、同様にＵＶ吸収原因物質が存在しており、ベーク後に残っていたとすると、露光光がレジスト底部まで充分に到達せず、不良パターンを起こす原因となる。
【０００４】
ＵＶ吸収原因物質の問題を解決する為に、例えば、特開平８−１２６２１号では、乳酸エチルを活性炭処理することにより、２８０ｎｍのＵＶ吸収が、１．０以下に低減出来ると提案されている。
【０００５】
【発明が解決しようとする課題】
ところが、活性炭処理を行うことにより、副生物である使用済みの活性炭が大量に出て、多額の再生費用あるいは廃棄物処理費用が必要となる。また、活性炭処理という工程によって原料液用と処理液用の貯槽が２つ必要となる。更に、活性炭処理のみでは、酸度の低減は僅かしか行われない。
【０００６】
【課題を解決する為の手段】
本発明者らは、前述の問題点を解決すべく、鋭意研究を重ねた結果、醗酵法により製造された乳酸エチル（以下醗酵乳酸エチルと云う）に２種類の添加剤を用い、蒸留精製することにより、酸度が低減され、且つ、２７０ｎｍ以上、４００ｎｍ以下のＵＶ吸光度が実質的に無視出来る程度まで低減された乳酸エチルが得られることを見い出し、本発明に到達したものである。
即ち、本発明は、醗酵乳酸エチルに予め一般式（１）
Ｒ^１−Ｎ＝Ｃ＝Ｎ−Ｒ^２（１）
［Ｒ^１及びＲ^２は、炭素数１〜８の残基であり、Ｒ^１＝Ｒ^２若しくはＲ^１≠Ｒ^２を満たすものである。］で表されるカルボジイミド類を投入し、酸度を低減しておき、それを一般式（２）

［ｎは１〜３の整数、Ｒ^３は水素または炭素数１〜８の残基または−ＯＲ^４（Ｒ^４は水素または炭素数１〜１２の残基）］で表されるアニリン誘導体の存在下、蒸留塔の塔底においてＵＶ吸収原因物質を反応させながら、蒸留することを特徴とする乳酸エチルの精製方法である。
或いは、醗酵乳酸エチルを一般式（２）で表されるアニリン誘導体の存在下、蒸留塔の塔底においてＵＶ吸収原因物質を反応させながら、蒸留することを特徴とする乳酸エチルの精製方法である。
【０００７】
本発明で使用されるカルボジイミド類としては、例えば、Ｎ，Ｎ’−ジシクロヘキシルカルボジイミド、Ｎ，Ｎ’−ジ−ｐ−トリルカルボジイミド等が挙げられる。これらカルボジイミド類は、カルボン酸と反応することは、文献から公知であるが、通常、アミノ酸からペプチドを合成する際に使用される。
【０００８】
本発明の方法に関わる酸度低減の為のカルボジイミド類添加は、醗酵乳酸エチルが入った貯槽中、蒸留塔中、或いは、その他の反応器中で行うことが出来、反応温度は、２０℃から１００℃までの間で行われる。但し、２０℃の場合は４８時間以上、７０℃の場合は１時間以上、また１００℃の場合は３０分以上の反応時間が必要である。２０℃以下では非常に長い反応時間が必要であり、また、１００℃以上では乳酸エチルが分解し、不純物であるエタノールが増加する場合がある。添加量に関しては、低減させたい酸度原因物質の量、例えば、乳酸に換算した当量の内、低減させたい酸度分と当量のカルボジイミド類を使用する。即ち、製品乳酸エチルの酸度が、カルボジイミド類の添加量により、コントロール出来る。
【０００９】
本発明で使用されるアニリン誘導体としては、例えば、アニリン、フェニレンジアミン、アミノフェノール、フェネチジン等が挙げられる。好ましくは乳酸エチルとの沸点差、安全性等の面からアミノフェノール、フェネチジンが望ましい。これら以外のアミン誘導体、例えば、脂肪族アミン類を使用すると、酸度低減やＵＶ吸光度低減が成されるが、乳酸エチルが分解され、エタノール等が発生する。
【００１０】
本発明の方法に関わるアニリン誘導体の存在下での蒸留法は、塔底の温度が６０℃から１００℃で行われる。６０℃以下では蒸留の分離が悪くなり、１００℃以上では乳酸エチルが分解や縮合を起こし、エタノールや乳酸ダイマーエステル等の不純物が発生する。添加量に関しては、精製する乳酸エチルの０．４ｗｔ％から１０ｗｔ％が望ましい。０．４ｗｔ％以下の添加量では、２８０ｎｍのＵＶ吸光度が、１を超える場合があり、１０ｗｔ％以上の添加量では、蒸留塔の塔底温度が１００℃を超え、乳酸エチルの分解が起こり、不純物であるエタノールが増加する場合がある。
蒸留精製の２バッチ目以降は、予めカルボジイミド類を投入し、酸度が低減された乳酸エチルを、前バッチの蒸留残留物に加える、バッチ連続的な蒸留精製が可能である。
【００１１】
更に、アニリン誘導体は、カルボジイミド類が酸と反応して生成した中間体と作用し、尿素とアミドを生成させる。カルボジイミド類を投入した乳酸エチルを、アニリン誘導体の存在なしで蒸留すると、対応する酸無水物が発生し易くなり、生成した酸無水物が乳酸エチルを分解し、結果的にエタノールが発生する。
【００１２】
本発明の更なる利点は、両添加剤による反応物や未反応アニリン誘導体が、全て蒸留時に塔底に残る為、よって蒸留留出液への混入を防げることである。また、本発明の方法は、各種エステル類においても、カルボン酸等の酸度原因物質やカルボニル化合物等のＵＶ吸収原因物質を除去する際、応用出来る。
【００１３】
【発明の実施の形態】
本発明の方法は、醗酵乳酸エチルに低減させたい酸度分と当量のカルボジイミド類を添加し、２０℃から１００℃の間で酸度を低減しておき、乳酸エチルの０．４ｗｔ％から１０ｗｔ％になる様、アニリン誘導体を添加し、蒸留する。蒸留条件は、塔底温度が６０℃から１００℃になる様、圧力を調整し、実施する。実施例として、以下に記載し、本発明を更に説明するが、本発明はこれらの実施例に限定されるものではない。
【００１４】
【実施例】
実施例１
醗酵乳酸エチル（純度９９．６８％（ＧＣ、以下省略）、酸度３６３ｐｐｍ（乳酸換算、以下省略）、ＵＶ吸光度４．７（２８０ｎｍ、以下省略））６０００ｇに、Ｎ，Ｎ’−ジシクロヘキシルカルボジイミド２．２６ｇを投入し、１０Ｌ反応器中において、室温で４８時間反応させた。４８時間後の酸度は、２０７ｐｐｍであった。
【００１５】
次に、この乳酸エチル７００ｇに、ｐ−フェネチジン３．７ｇを投入し、段数３段相当の蒸留塔で塔底温度６５〜７０℃、圧力４ｋＰａの条件において蒸留し、純度９９．９７％、酸度１１１ｐｐｍ、ＵＶ吸光度０．３、エタノール分７０ｐｐｍ（ＧＣ、以下省略）の乳酸エチルを４８２．１ｇ得た。
【００１６】
実施例２
実施例１で作製した酸度を低減させた乳酸エチル（以下酸度低減乳酸エチルと云う）５８８．３ｇを、実施例１の蒸留塔底残留物全量１１０．２ｇに加え、実施例１と同様の条件で蒸留を実施し、純度９９．９６％、酸度１１４ｐｐｍ、ＵＶ吸光度０．５、エタノール分６２ｐｐｍの乳酸エチルを４８４．０ｇ得た。
【００１７】
実施例３
実施例２の蒸留塔底残留物全量９９．２ｇに酸度低減乳酸エチル５９６．７ｇを加え、実施例１と同様の条件で蒸留を実施し、純度９９．９３％、酸度１３１ｐｐｍ、ＵＶ吸光度０．７、エタノール分５６ｐｐｍの乳酸エチルを４９４．４ｇ得た。
【００１８】
実施例４
醗酵乳酸エチル（純度９９．８５％、酸度２３９ｐｐｍ、ＵＶ吸光度１１．３）６００．１ｇにＮ，Ｎ’−ジシクロヘキシルカルボジイミド０．１２ｇを投入し、蒸留塔中において、７０℃で１時間反応させた。反応後の酸度は、１５８ｐｐｍであった。それに３−アミノフェノールを２．６ｇ添加し、実施例１と同様の条件で蒸留を実施し、純度９９．９１％、酸度１０４ｐｐｍ、ＵＶ吸光度０．７、エタノール分３６０ｐｐｍの乳酸エチルを４８３．９ｇ得た。
【００１９】
実施例５
醗酵乳酸エチル（純度９９．８１％、酸度２０４ｐｐｍ、ＵＶ吸光度７．３）６００．３ｇにｐ−フェネチジン２．４ｇを投入し、実施例１と同様の条件で蒸留を実施し、純度９９．９２％、酸度１２５ｐｐｍ、ＵＶ吸光度０．３、エタノール分２８５ｐｐｍの乳酸エチルを４９９．５ｇ得た。
【００２０】
比較例１
醗酵乳酸エチル（純度９９．７８％、酸度４１３ｐｐｍ、ＵＶ吸光度６．０）６００．４ｇのみを、実施例１と同様の条件で蒸留を実施し、純度９９．９７％、酸度２３３ｐｐｍ、ＵＶ吸光度６．０、エタノール分３２ｐｐｍの乳酸エチルを３３６．９ｇ得た。蒸留原料である醗酵乳酸エチルに比べ、酸度は半減のみで、更にＵＶ吸光度は低減されなかった。
【００２１】
比較例２
醗酵乳酸エチル（純度９９．９３％、酸度２７３ｐｐｍ、ＵＶ吸光度１１．４）８３６．９ｇに４８％水酸化ナトリウム水溶液０．２ｇを投入し、実施例１と同様の条件で蒸留を実施し、純度９９．８５％、酸度４３ｐｐｍ、ＵＶ吸光度１０．９、エタノール分１３３６ｐｐｍの乳酸エチルを６２６．０ｇ得た。蒸留原料である醗酵乳酸エチルに比べ、酸度は低減されているものの、分解が生じ、多量のエタノールが発生した。
【００２２】
比較例３
醗酵乳酸エチル（純度９９．６３％、酸度８７５ｐｐｍ、ＵＶ吸光度２０．０）７００．０ｇにステアリルアミン６．９ｇを投入し、実施例１と同様の条件で蒸留を実施し、純度９９．８０％、酸度１１８ｐｐｍ、ＵＶ吸光度０．８、エタノール分１３３４ｐｐｍの乳酸エチルを５３１．９ｇ得た。蒸留原料である醗酵乳酸エチルに比べ、酸度及びＵＶ吸光度が低減されているものの、分解が生じ、多量のエタノールが発生した。
【００２３】
比較例４
醗酵乳酸エチル（純度９９．９５％、酸度５６４ｐｐｍ、ＵＶ吸光度３．７）６０２．４ｇに、３−アミノフェノールを醗酵乳酸エチルの０．１ｗｔ％である０．６ｇ投入し、実施例１と同様の条件で蒸留を実施し、純度９９．９９％、酸度４２９ｐｐｍ、ＵＶ吸光度１．３、エタノール分不検出の乳酸エチルを４４４．８ｇ得た。
【００２４】
【発明の効果】
本発明の方法によれば、酸度の低い、且つ、２７０ｎｍ以上、４００ｎｍ以下のＵＶ吸光度が実質的に無視出来る程度まで低減された高純度の乳酸エチルを、簡単な工程で、且つ低コストで得られる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a photoresist solvent characterized by reducing acidity in ethyl lactate produced by fermentation and UV absorbance of 270 nm or more and 400 nm or less by distillation using carbodiimides and aniline derivatives. It is related with the refinement | purification method of ethyl lactate useful as. Alternatively, the present invention relates to a method for purifying ethyl lactate, wherein the UV absorbance at 270 nm or more and 400 nm or less is reduced by distillation of fermented ethyl lactate in the presence of an aniline derivative.
[0002]
[Prior art]
Ethyl lactate is used as a photoresist resin solvent that is used in a wide range of fields such as semiconductor devices, printed wiring boards, and printing plates that are manufactured using lithography technology. However, the disadvantage of ethyl lactate produced by fermentation is the presence of trace amounts of impurities, such as acidity-causing substances such as acetic acid and lactic acid, and UV-absorbing substances such as various carbonyl compounds. However, it cannot be substantially removed by conventional purification means such as simple distillation.
[0003]
If the acidity-causing substance is present in the positive photoresist resin solvent and does not evaporate during baking and is concentrated, the unexposed area can be dissolved by a developer such as an alkaline aqueous solution, resulting in a defective pattern. There is sex. Similarly, if a UV absorption-causing substance exists and remains after baking, the exposure light does not reach the bottom of the resist sufficiently, causing a defective pattern.
[0004]
In order to solve the problem of UV absorption-causing substances, for example, JP-A-8-12621 proposes that UV absorption at 280 nm can be reduced to 1.0 or less by treating activated carbon with ethyl lactate.
[0005]
[Problems to be solved by the invention]
However, when activated carbon treatment is performed, a large amount of used activated carbon, which is a by-product, comes out, and a large amount of regeneration costs or waste disposal costs are required. Further, two storage tanks for the raw material liquid and the processing liquid are required by a process called activated carbon treatment. Furthermore, only the activated carbon treatment reduces the acidity only slightly.
[0006]
[Means for solving the problems]
As a result of intensive studies to solve the above-mentioned problems, the present inventors use two types of additives in ethyl lactate produced by the fermentation method (hereinafter referred to as fermented ethyl lactate) and perform distillation purification. As a result, it was found that ethyl lactate having a reduced acidity and a UV absorbance of 270 nm or more and 400 nm or less was substantially reduced to a negligible level, and the present invention has been achieved.
That is, the present invention relates to the general formula (1)
R ¹ —N═C═N—R ² (1)
[R ¹ and R ² are residues having 1 to 8 carbon atoms and satisfy R ¹ = R ² or R ¹ ≠ R ² . The carbodiimides represented by general formula (2) are reduced by adding acidity.

Presence of an aniline derivative represented by [n is an integer of 1 to 3, R ³ is hydrogen, a residue having 1 to 8 carbon atoms, or —OR ⁴ (R ⁴ is hydrogen or a residue having 1 to 12 carbon atoms)] The following is a method for purifying ethyl lactate, characterized in that distillation is performed while reacting a UV-absorbing substance at the bottom of the distillation column.
Alternatively, the method is a method for purifying ethyl lactate, which comprises distilling fermented ethyl lactate in the presence of an aniline derivative represented by the general formula (2) while reacting a UV-absorbing substance at the bottom of the distillation column. .
[0007]
Examples of the carbodiimides used in the present invention include N, N′-dicyclohexylcarbodiimide, N, N′-di-p-tolylcarbodiimide and the like. Although it is known from the literature that these carbodiimides react with carboxylic acids, they are usually used when synthesizing peptides from amino acids.
[0008]
Addition of carbodiimides for acidity reduction related to the method of the present invention can be carried out in a storage tank containing fermented ethyl lactate, in a distillation column, or in another reactor, and the reaction temperature is from 20 ° C to 100 ° C. It is carried out between up to ° C. However, a reaction time of 48 hours or longer is required at 20 ° C., 1 hour or longer at 70 ° C., and 30 minutes or longer at 100 ° C. At 20 ° C. or lower, a very long reaction time is required. At 100 ° C. or higher, ethyl lactate is decomposed and ethanol as an impurity may increase. Regarding the amount added, carbodiimides equivalent to the acidity to be reduced are used in the amount of the acidity-causing substance to be reduced, for example, the equivalent in terms of lactic acid. That is, the acidity of the product ethyl lactate can be controlled by the amount of carbodiimide added.
[0009]
Examples of aniline derivatives used in the present invention include aniline, phenylenediamine, aminophenol, phenetidine and the like. Preferably, aminophenol and phenetidine are desirable from the viewpoint of boiling point difference from ethyl lactate, safety and the like. When amine derivatives other than these, for example, aliphatic amines are used, the acidity and UV absorbance are reduced, but ethyl lactate is decomposed to generate ethanol and the like.
[0010]
The distillation method in the presence of the aniline derivative involved in the method of the present invention is carried out at a column bottom temperature of 60 ° C to 100 ° C. At 60 ° C. or lower, distillation separation becomes poor, and at 100 ° C. or higher, ethyl lactate decomposes or condenses, and impurities such as ethanol and lactic acid dimer ester are generated. Regarding the addition amount, 0.4 wt% to 10 wt% of the ethyl lactate to be purified is desirable. When the addition amount is 0.4 wt% or less, the UV absorbance at 280 nm may exceed 1, and when the addition amount is 10 wt% or more, the bottom temperature of the distillation column exceeds 100 ° C., and decomposition of ethyl lactate occurs. Impurity ethanol may increase.
From the second batch of distillation purification, carbodiimides are added in advance, and ethyl lactate with reduced acidity is added to the distillation residue of the previous batch, and batch continuous distillation purification is possible.
[0011]
Furthermore, the aniline derivative acts with an intermediate formed by the reaction of carbodiimides with an acid to generate urea and amide. When ethyl lactate charged with carbodiimides is distilled without the presence of an aniline derivative, the corresponding acid anhydride is likely to be generated, and the produced acid anhydride decomposes ethyl lactate, resulting in generation of ethanol.
[0012]
A further advantage of the present invention is that all reactants and unreacted aniline derivatives from both additives remain at the bottom of the column during distillation, thus preventing contamination in the distillation distillate. The method of the present invention can also be applied to various esters to remove acidity-causing substances such as carboxylic acids and UV-absorbing substances such as carbonyl compounds.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
In the method of the present invention, carbodiimides equivalent to the acidity to be reduced are added to fermented ethyl lactate, and the acidity is reduced between 20 ° C. and 100 ° C., and the ethyl lactate is reduced from 0.4 wt% to 10 wt%. Add an aniline derivative and distill. Distillation is carried out by adjusting the pressure so that the column bottom temperature is 60 ° C to 100 ° C. The present invention will be further described below by way of examples. However, the present invention is not limited to these examples.
[0014]
【Example】
Example 1
To 6000 g of fermented ethyl lactate (purity 99.68% (GC, hereinafter omitted), acidity 363 ppm (lactic acid conversion, hereinafter omitted), UV absorbance 4.7 (280 nm, hereinafter omitted)), N, N′-dicyclohexylcarbodiimide 2. 26 g was charged and reacted in a 10 L reactor at room temperature for 48 hours. The acidity after 48 hours was 207 ppm.
[0015]
Next, 3.7 g of p-phenetidine was added to 700 g of this ethyl lactate, and distilled at a bottom temperature of 65 to 70 ° C. and a pressure of 4 kPa in a distillation column corresponding to three stages, purity 99.97%, acidity 482.1 g of ethyl lactate having 111 ppm, UV absorbance of 0.3 and ethanol content of 70 ppm (GC, hereinafter omitted) was obtained.
[0016]
Example 2
588.3 g of ethyl lactate with reduced acidity (hereinafter referred to as reduced acidity ethyl lactate) prepared in Example 1 was added to 110.2 g of the total distillation column bottom residue of Example 1, and the same conditions as in Example 1 Distillation was performed to obtain 484.0 g of ethyl lactate having a purity of 99.96%, acidity of 114 ppm, UV absorbance of 0.5, and ethanol content of 62 ppm.
[0017]
Example 3
596.7 g of ethyl lactate with reduced acidity was added to 99.2 g of the total residue at the bottom of the distillation column of Example 2, and distillation was carried out under the same conditions as in Example 1. The purity was 99.93%, the acidity was 131 ppm, and the UV absorbance was 0.00. 7. 494.4 g of ethyl lactate having an ethanol content of 56 ppm was obtained.
[0018]
Example 4
N, N′-dicyclohexylcarbodiimide 0.12 g was added to 600.1 g of fermented ethyl lactate (purity 99.85%, acidity 239 ppm, UV absorbance 11.3), and reacted in a distillation column at 70 ° C. for 1 hour. . The acidity after the reaction was 158 ppm. 2.6 g of 3-aminophenol was added thereto, and distillation was carried out under the same conditions as in Example 1. 483.9 g of ethyl lactate having a purity of 99.91%, acidity of 104 ppm, UV absorbance of 0.7, and ethanol content of 360 ppm. Obtained.
[0019]
Example 5
2.4 g of p-phenetidine was added to 600.3 g of fermented ethyl lactate (purity 99.81%, acidity 204 ppm, UV absorbance 7.3), and distillation was carried out under the same conditions as in Example 1 to obtain a purity of 99.92. %, 499.5 g of ethyl lactate having an acidity of 125 ppm, a UV absorbance of 0.3, and an ethanol content of 285 ppm.
[0020]
Comparative Example 1
Only 600.4 g of fermented ethyl lactate (purity 99.78%, acidity 413 ppm, UV absorbance 6.0) was distilled under the same conditions as in Example 1, purity 99.97%, acidity 233 ppm, UV absorbance 6 0.06.9 Ethyl lactate having an ethanol content of 32 ppm was obtained. Compared with fermented ethyl lactate which is a raw material for distillation, the acidity was only halved, and the UV absorbance was not further reduced.
[0021]
Comparative Example 2
Fermentation ethyl lactate (purity 99.93%, acidity 273 ppm, UV absorbance 11.4) 836.9 g was charged with 0.2 g of 48% aqueous sodium hydroxide and distilled under the same conditions as in Example 1 626.0 g of ethyl lactate having 99.85%, acidity of 43 ppm, UV absorbance of 10.9 and ethanol content of 1336 ppm was obtained. Although the acidity was reduced compared to fermented ethyl lactate as a distillation raw material, decomposition occurred and a large amount of ethanol was generated.
[0022]
Comparative Example 3
6.9 g of stearylamine was added to 700.0 g of fermented ethyl lactate (purity 99.63%, acidity 875 ppm, UV absorbance 20.0), and distillation was carried out under the same conditions as in Example 1. Purity 99.80% Thus, 531.9 g of ethyl lactate having an acidity of 118 ppm, a UV absorbance of 0.8, and an ethanol content of 1334 ppm was obtained. Although acidity and UV absorbance were reduced compared to fermented ethyl lactate as a distillation raw material, decomposition occurred and a large amount of ethanol was generated.
[0023]
Comparative Example 4
As in Example 1, 0.6 g, which is 0.1 wt% of fermented ethyl lactate, is added to 602.4 g of fermented ethyl lactate (purity 99.95%, acidity 564 ppm, UV absorbance 3.7). Distillation was carried out under the following conditions to obtain 444.8 g of ethyl lactate having a purity of 99.99%, an acidity of 429 ppm, a UV absorbance of 1.3, and no ethanol content detected.
[0024]
【Effect of the invention】
According to the method of the present invention, high purity ethyl lactate having a low acidity and a UV absorbance of 270 nm or more and 400 nm or less reduced to a substantially negligible level can be obtained in a simple process and at a low cost. It is done.

Claims

Ethyl lactate produced by fermentation, carbodiimides selected from N, N'-dicyclohexylcarbodiimide and N, N'-di-p- tolylcarbodiimide, and aniline derivatives selected from aniline, phenylenediamine, aminophenol and phenetidine by distillation was added to acidity in milk ethyl, and 270nm or more, the purification method of the ethyl lactate, characterized in that to reduce the following UV absorbance 400 nm.

Ethyl lactate that reduces UV absorbance at 270 nm to 400 nm of ethyl lactate produced by fermentation by distillation in the presence of an aniline derivative selected from aniline, phenylenediamine, aminophenol, and phenetidine Purification method.

The method for purifying ethyl lactate according to claim 1, wherein the amount of carbodiimide added is equivalent to the acid content to be reduced in ethyl lactate , and the reaction temperature of the carbodiimide and the acid content is 20 ° C to 100 ° C. .

The method for purifying ethyl lactate according to claim 1 or 2, wherein the addition amount of the aniline derivative is 0.4 wt% to 10 wt% of ethyl lactate.

The method for purifying ethyl lactate according to any one of claims 1 to 4 , wherein the bottom temperature of the distillation column is 60 ° C to 100 ° C.